Stop Making NPCs Talk. Make Them Lie.

I was on holiday in Sicily. Waiting for a train in Palermo, I fancied a game to while away an hour or two. My relaxed brain dropped into creative mode: I hadn't seen any AI games where AI was really the core of the experience. Lots of demos of NPCs chatting. Nothing I actually wanted to play.

Text chat is where LLMs excel, so a game built on correspondence made sense. A murder mystery seemed like the right challenge — characters who each hold a piece of the truth, who need to stay consistent, who have reasons to lie. Being no author, I wanted rich source material — not some hollow AI-generated character with no backstory, no internal life. I found Wilkie Collins' The Moonstone (1868), widely considered the first detective novel in English. The whole book is told through letters and testimony. Perfect.

I set Claude off to make a simple prototype on my phone, on the train. Before I arrived an hour later I had a basic game where I could correspond with characters about the mystery. Did it work? No. The characters had absorbed the entire complex plot and it was unplayable. But it was clear something was possible.

The wrong problem

The AI games industry is obsessed with making NPCs talk. But talking isn't interesting. Having something to hide is interesting.

Most AI NPC experiments bolt conversation onto existing game structures. Walk up to a shopkeeper, have a freeform chat, buy your sword, move on. The AI replaces a UI element. It doesn't change the game. Asking the blacksmith about his childhood doesn't make the sword sharper.

Everyone's using AI to do the same thing slightly better — replacing dialogue trees with freeform chat. That's AI as the interface. The question I kept coming back to: what game can only exist because of AI? What experience is impossible without it?

Making it real

That broken prototype on the train was the starting point. Making it playable was a different problem entirely.

The key iteration was the Story Bible. I needed to carefully construct the timeline of events, each character's knowledge and motivations, what they'd witnessed, what they were hiding and why. Then convert all of that into specific prompts that gave each character enough context to be consistent but enough freedom to surprise me. Six characters, each with their own slice of the truth, their own loyalties, their own reasons to mislead you.

Then playtesting. Over and over, looking for inconsistencies — moments where a character would reveal something they shouldn't know, or contradict what another had said. Ironing those out was the real work. Not the code. The narrative engineering.

What came out the other side is The Moonstone — a React web app where you play a detective investigating a murder at a Victorian country estate, corresponding with six suspects by letter. It's hosted on Vercel, with authentication, payment integration, end-to-end testing, admin tooling. A proper product, not just a prototype. But the technology isn't the point. The characters are.

Characters that lie to you

The most interesting thing I found wasn't the technology. It was the deception.

Some characters are protecting others. Some are embarrassed by their own actions. Some are genuinely confused about what happened. You have to win them over, help them see things in a different light, or just treat them with empathy to get the information you need. You're not selecting dialogue options. You're reading people.

Take Rachel. She stonewalls you. It's clear she knows something but she won't share it. Who is she protecting, and why? Once you crack that — once you work out the truth of what happened and offer her a whole new perspective on events — she retreads everything in her own mind and comes to conclusions that help you solve the mystery. That's an emotional arc, not a puzzle mechanic. And it's an experience that cannot exist without AI — no dialogue tree can model that kind of human dynamic.

This is what I mean by AI as the game, not AI as the interface. You're not chatting with an NPC to get a quest marker. You're navigating a group of people with competing loyalties, working around the human dynamics between them, and figuring out who's lying about what.

API costs became the game clock

LLMs cost money — at least the good ones. The cheap or self-hosted models don't have the horsepower for convincing deception. So I needed to control how much a single player could spend on a playthrough.

At first I was going to show a raw token budget that depleted as you played. Then I realised: linking it to in-game time adds a natural mechanic. Challenge. Urgency. Stakes.

Time ticks by with every exchange — by the minute, by the hour, by the day. In polite Victorian fashion, each letter comes with a timestamp (back in the day there were multiple postal deliveries a day). As you get down to the last few days, your boss starts writing to you, setting out expectations to report back to the magistrate. The pressure comes from the world, not a progress bar. A genuine constraint became a genuine feature.

The positioning paradox

I posted the game on r/interactivefiction — the community you'd expect to be most enthusiastic about a freeform mystery. The mods removed it for using AI.

On r/playmygame, the comments said it sounded "really interesting" and a "genuinely creative use of AI" — but that people would probably ignore it because of the AI.

The people who'd love the experience reject the technology. The people who appreciate the technology aren't looking for a Victorian murder mystery.

I realised I didn't want to call it "an AI game" — at least not to players. The AI that powers it should matter no more than whether you used Unity behind the scenes. It's just a game. But AI has lowered the barrier to getting ideas out, which has overwhelmed communities with generic, low-quality games — especially in the text-based world. I hope mine is different. But maybe that's what everyone says.

The tension is real and I don't think it resolves easily. The AI is integral to the mechanics. It's the reason the experience exists at all. I just don't think leading with "AI-powered" is the way to find the people who'd actually enjoy it.

Where this goes

I've been thinking about harnesses for AI. I was listening to the creators of Claude Code talking about the effectiveness that was unlocked by putting a specialised harness around the model. Not improving the AI itself, but building the right structure around it so it could do something specific really well.

I think the same applies to entertainment. The breakthrough won't be a better chatbot or a more realistic NPC. It'll be a harness — a specialised structure that creators can pour their vision and world into, with AI enabling the experience underneath.

That's what I ended up building, even if I didn't set out to. The Story Bible, the character prompts, the timeline management, the pacing of revelation — that's a framework. Something a writer could use to create their own mystery for players to explore, without needing to anticipate every possible conversation. The AI handles the infinite surface area of human interaction. The creator handles the story, the characters, the truth.

Nobody cares what engine a game runs on. They care if it's fun. I think the breakthrough AI entertainment product won't announce itself as AI-powered. It'll just be an experience that couldn't exist any other way.